[Mocha] Fix transports not stopping when the host shuts down

[tobias-tengler]

When the host shut down, MessagingRuntimeHostedService.StopAsync only disposed the consumers. The transports kept receiving and heartbeating, even after the service provider was disposed. Messages picked up after shutdown failed on the disposed consumers.

This PR adds MessagingRuntime.StopAsync, which stops the started transports, and the hosted service calls it instead of disposing the runtime. Disposing the runtime now stops and disposes its transports. A stopped runtime cannot be started again, so StartAsync throws after StopAsync. The PostgreSQL transport stops its background tasks in a new OnAfterStopAsync hook, so its consumer stays registered until the endpoints have stopped.

[github-actions]

Patch coverage

100.0% of changed lines covered (30/30)

File	Covered	Changed	Patch %
src/Mocha/src/Mocha/Runtime/MessagingRuntime.cs	27	27	100.0% 🟢
src/Mocha/src/Mocha/Runtime/MessagingRuntimeHostedService.cs	1	1	100.0% 🟢
src/Mocha/src/Mocha/Transport/MessagingTransport.cs	2	2	100.0% 🟢

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Project coverage: 58.6% (314103/536388 lines)

[Copilot]

Copilot review overview

🟡 Changes recommended

Shutdown failure handling and shared-batch cancellation can leave endpoints active or misclassify cancellation as message failure.

Review effort: Balanced
Findings: 3 · 1 · 1

Open (5)

• Make batch enqueue cancellation-aware · New
• Continue stopping transports after individual shutdown failures · New
• Do not mark transport stopped while endpoints remain active · New
• Handle shutdown cancellation without failure telemetry · New
• Reduce test assertions to repository limit · New

What changed in this PR

Fixes Mocha shutdown behavior by stopping transports, propagating cancellation to handlers, and cleaning up resources.

Changes:

• Adds runtime and transport shutdown lifecycle handling.
• Propagates cancellation through receive, retry, and batch pipelines.
• Adds shutdown, retry, and batching tests.

File	Description
Mocha.Transport.RabbitMQ.Tests/​Behaviors/​ShutdownTests.cs	Tests cancellation and message requeue.
Mocha.Transport.Postgres.Tests/​Behaviors/​ShutdownTests.cs	Tests lease preservation during shutdown.
Mocha.Tests/​Runtime/​MessagingRuntimeShutdownTests.cs	Tests endpoint and batch cancellation.
Mocha.Tests/​Middlewares/​Consume/​Retry/​RetryExecutorTests.cs	Tests cancellation-aware retries.
Mocha.Tests/​Consumers/​Batching/​BatchCollectorTests.cs	Tests buffered-entry removal.
Mocha/​Transport/​MessagingTransport.cs	Stops endpoints before transport cleanup.
Mocha/​Runtime/​MessagingRuntimeHostedService.cs	Stops runtime with the host.
Mocha/​Runtime/​MessagingRuntime.cs	Adds runtime shutdown and transport disposal.
Mocha/​Middlewares/​ReceiveContext.cs	Assigns receive cancellation tokens.
Mocha/​Middlewares/​Receive/​Redelivery/​ReceiveRedeliveryMiddleware.cs	Skips redelivery during cancellation.
Mocha/​Middlewares/​Receive/​ReceiveFaultMiddleware.cs	Skips fault handling during cancellation.
Mocha/​Middlewares/​Receive/​ReceiveDeadLetterMiddleware.cs	Skips dead-letter handling during cancellation.
Mocha/​Middlewares/​Consume/​Retry/​RetryExecutor.cs	Stops retries after cancellation.
Mocha/​Endpoints/​ReceiveEndpoint.cs	Propagates cancelled processing.
Mocha/​Consumers/​Implementations/​BatchConsumer.cs	Links batch and endpoint cancellation.
Mocha/​Consumers/​Batching/​BatchCollector.cs	Removes cancelled buffered entries.
Mocha.Transport.RabbitMQ/​Connection/​RabbitMQConsumerManager.cs	Cancels handlers before disconnecting.
Mocha.Transport.Postgres/​PostgresMessagingTransport.cs	Defers cleanup until endpoints stop.

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